The present invention relates to a novel method and means for decoding a high density multiple bar code from a record medium at a high rate of speed and more particularly, relates to an NMOS/LSI chip which receives both valid and invalid data from a pattern recognition chip and extracts only the data which is valid. This valid data is then transmitted to a microprocessor for assembling into a readable form.
The use of bar coded symbols or labels intended to be read by optical scanning equipment as a means for identifying new data useful in processing items sold in the retail industry has been widely accepted to the point that a particular bar code known as the Universal Product Code (UPC) has been established as the industry standard for the grocery and other related retail industries. In the multiple bar code, such as the UPC, each decimal number or character is represented by two pairs of vertical bars and spaces within a 7-bit pattern wherein a binary 1 bit represents a dark module or bar of a predetermined width and a binary 0 represents a light module or space. Thus, the decimal or character 1 may be represented in the UPC code by the 7-bit pattern 0011001. In keeping with the format, the decimal 1 would be comprised of an initial space of a 2-bit width, followed by a 2-bit wide bar, another 2-bit space and a 1-bit wide bar. For each character or decimal of the system there are two bars and two spaced which have a total width of seven modules or bits. The width of each of the bars or spaces which comprise a character may be 1, 2, 3 or 4 modules wide as long as the sum of the bars and spaces is seven bits or modules wide.
A multiple bar code, such as the UPC, is normally read by an optical scanner whih may take the form of a hand-held wand or a scanner mechanism located in a check-out counter. The optical scanner will scan the bar code pattern and generate signals representing the bafs and space for transmission to the processing apparatus which determines the character represented by the bar code pattern.
Prior optical readers generally store the electrical signals generated as a result of scanning the bar code pattern until the accumulated signals stored are sufficient to allow the processing apparatus to initiate a recognition operation to determine the character represented by the scanned bar code pattern. Because of the speed in which the scanning operation is performed, the cost of the prior optical readers in processing the electrical signals has been unduly expensive, which in many instances has prevented the readers from reaching the marketplace. It is therefore the principal object of this invention to provide a low-cost optical character reader. It is another object of this invention to provide a low-cost optical character reader system which operates at a relatively high rate of speed without a loss of recognition efficiency. It is a further object of this invention to provide a system for filtering out invalid data embodied in an NMOS/LSI chip.